High Humidity Sparks December Blackout in San Francisco
An independent investigation has revealed that high humidity levels inside PG&E's Mission substation were a key factor in a December blackout that left 120,000 San Francisco residents without power. The probe, conducted by engineering firm Exponent, found that condensation buildup caused by elevated humidity led to a fire in the substation's switchgear room. The substation, built in the 1940s, lacked proper drainage and ventilation systems, exacerbating the issue. PG&E had identified damaged equipment prior to the incident but failed to address it adequately. The blackout disrupted daily life, with residents unable to flush toilets, businesses losing revenue, and holiday events being canceled. 
